Many materials, such as wood chips, grain, shredded garbage, and like divided materials, are conveniently conveyed by entraining the same in the air-stream of a pneumatic conveying line. To prevent the escape of air into or out of such conveying line, the divided material is commonly fed into the line by means of a rotary air-lock device. Typically, such devices have comprised a cylindrical housing mounted over a conveying line and formed with an outlet opening directly into the line. Mounted in the housing is a rotor comprising a plurality of helically shaped blades adapted to engage the periphery of the housing and to form with the housing as they rotate sealed chambers for conveying material from an upper inlet to the outlet. The upper edge of the housing is provided with a shearing knife which, with the edge of a rotor blade, forms a shear to cut off material projecting beyond the edge of a rotor blade as it rotates beneath the knife. This is done to protect the housing wall from abrasion by such material or binding by the same. Periodically, the rotor blades must be sharpened. This has required dismantling of the housing and removal of the blades.